Cochlear implants including electrode arrays and methods of making the same

ABSTRACT

A method of forming an electrode array includes the steps of positioning a workpiece on a mold part, compressing the workpiece into the mold part to form a contact, and introducing resilient material into the mold part to form a flexible body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage of PCT App. Ser. No.PCT/US2016/046621, filed Aug. 11, 2016.

BACKGROUND 1. Field

The present disclosure relates generally to the implantable portion ofimplantable cochlear stimulation (or “ICS”) systems and, in particular,to electrode arrays.

2. Description of the Related Art

ICS systems are used to help the profoundly deaf perceive a sensation ofsound by directly exciting the intact auditory nerve with controlledimpulses of electrical current. Ambient sound pressure waves are pickedup by an externally worn microphone and converted to electrical signals.The electrical signals, in turn, are processed by a sound processor,converted to a pulse sequence having varying pulse widths, rates, and/oramplitudes, and transmitted to an implanted receiver circuit of the ICSsystem. The implanted receiver circuit is connected to an implantablelead with an electrode array that is inserted into the cochlea of theinner ear, and electrical stimulation current is applied to varyingelectrode combinations to create a perception of sound. The electrodearray may, alternatively, be directly inserted into the cochlear nervewithout residing in the cochlea. A representative ICS system isdisclosed in U.S. Pat. No. 5,824,022, which is entitled “CochlearStimulation System Employing Behind-The-Ear Sound processor With RemoteControl” and incorporated herein by reference in its entirety. Examplesof commercially available ICS sound processors include, but are notlimited to, the Advanced Bionics™ Harmony™ BTE sound processor, theAdvanced Bionics™ Naida™ BTE sound processor and the Advanced Bionics™Neptune™ body worn sound processor.

As alluded to above, some ICS systems include an implantable cochlearstimulator (or “cochlear implant”) having a lead with an electrodearray, a sound processor unit (e.g., a body worn processor orbehind-the-ear processor) that communicates with the cochlear implant,and a microphone that is part of, or is in communication with, the soundprocessor unit. The cochlear implant electrode array, which is formed bya molding process, includes a flexible body formed from a resilientmaterial such as liquid silicone rubber (“LSR”) and a plurality ofelectrically conductive contacts (e.g., sixteen platinum contacts)spaced along a surface of the flexible body. The contacts of the arrayare connected to lead wires that extend through the flexible body. Onceimplanted, the contacts face the modiolus within the cochlea.

The present inventors have determined that conventional methods ofmanufacturing electrode arrays are susceptive to improvement. Theelectrically conductive contacts, which must have a clean exposedsurface to function properly, are masked during the molding process toprevent the LSR or other resilient material from covering the contacts.In some conventional processes, the contacts are welded to an iron stripand connected to the lead wires. The iron strip masks portions of thecontacts. The contacts, iron strip and lead wires are then placed into amold that is configured to accommodate the iron strip. Resilientmaterial is injected into the mold to form the flexible body of theelectrode array through an overmolding process. The electrode array isremoved from the mold once the resilient material has cured. The ironstrip is then etched away from the contacts, in a bath of nitric acid orhydrochloric acid, thereby exposing the contacts. The contacts must becleaned after the acid bath. The acid bath and cleaning takeapproximately 8 hours. The present inventors have determined that itwould be desirable to avoid the use of harsh chemicals and theproduction delay associated therewith. The present inventors have alsodetermined that welded masks can result in an uneven and uncontrolledcontact surface, with small granulations in surface structure, which ismore likely to experience biofilm and fibrous tissue growth than asmooth surface. Irregular surfaces are also likely to result inelectrical impedances that vary from contact to contact.

SUMMARY

A method in accordance with one of the present inventions includes thesteps of positioning a workpiece on a mold part such that a portion ofthe workpiece is within a channel of the mold part, compressing theworkpiece to form a contact, and introducing resilient material into thechannel to form a flexible body. There are a number of advantagesassociated with such a method. For example, the surface of the channelmasks the outer surface of the contacts from the resilient material,thereby eliminating the need for welded masks and etching associatedwith some conventional methods. The present method also produces asmooth, clean surface that is less likely to experience biofilm andfibrous tissue grown after implantation or electrical impedances thatvary from contact to contact.

A cochlear implant in accordance with one of the present inventions mayhave a housing, an antenna, a stimulation processor, and an electrodearray, operably connected to the stimulation processor, including aflexible body defining a longitudinal axis and a truncated circle shapein a cross-section perpendicular to the longitudinal axis, and aplurality of electrically conductive contacts on the flexible body.There are a number of advantages associated with such an implant. Forexample, the truncated circle shape may have a flat surface that ispositioned against the lateral wall during insertion of the electrodearray into the cochlea, thereby preventing twisting of the electrodearray.

A method in accordance with one of the present inventions comprisesinserting an electrode array, including a flexible body, defining alongitudinal axis and a truncated circle shape with a flat surface in across-section perpendicular to the longitudinal axis, and a plurality ofelectrically conductive contacts on the flexible body, into a cochleawith a lateral wall in such a manner that at least a portion of the flatsurface engages the lateral wall during insertion.

The above described and many other features of the present inventionswill become apparent as the inventions become better understood byreference to the following detailed description when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed descriptions of the exemplary embodiments will be made withreference to the accompanying drawings.

FIG. 1 is a plan view of a cochlear implant in accordance with oneembodiment of a present invention.

FIG. 2 is a perspective view of a portion of the cochlear leadillustrated in FIG. 1.

FIG. 3 is a perspective view of a portion of the cochlear leadillustrated in FIG. 1.

FIG. 4 is a bottom view of a portion of the cochlear lead illustrated inFIG. 1.

FIG. 4A is a section view taken along line 4A-4A in FIG. 4.

FIG. 4B is a section view taken along line 4B-4B in FIG. 4.

FIG. 5 is a plan view of a mold in accordance with one embodiment of apresent invention.

FIG. 5A is a section view taken along line 5A-5A in FIG. 5.

FIG. 5B is an enlarged view of a portion of FIG. 5A.

FIG. 6 is a plan view of a portion of a molding process in accordancewith one embodiment of a present invention.

FIG. 7 a section view taken along line 7-7 in FIG. 6.

FIG. 7A is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 7B is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 7C is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 7D is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 8 is a partial section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 9 is a plan view of a portion of a molding process in accordancewith one embodiment of a present invention.

FIG. 10 is a plan view of a portion of a molding process in accordancewith one embodiment of a present invention.

FIG. 11 is a plan view of a portion of a molding process in accordancewith one embodiment of a present invention.

FIG. 12 a section view taken along line 12-12 in FIG. 11.

FIG. 13 is an enlarged view of a portion of FIG. 11.

FIG. 14 is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 15 is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 15A is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 16 is a section view of an electrode assembly in accordance withone embodiment of a present invention.

FIG. 17 is a flow chart showing a method in accordance with oneembodiment of a present invention.

FIG. 18 is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 19 is a section view of an electrode assembly in accordance withone embodiment of a present invention.

FIG. 20 is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 21 is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 22 is a section view of an electrode assembly in accordance withone embodiment of a present invention.

FIG. 23 is a section view of the electrode assembly illustrated in FIGS.1-4B positioned within a cochlea.

FIG. 24 is a section view of a portion of a molding process inaccordance with one embodiment of a present invention.

FIG. 25 is a section view of an electrode assembly in accordance withone embodiment of a present invention.

FIG. 26 is a section view of the electrode assembly illustrated in FIGS.24 and 25 positioned within a cochlea.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The following is a detailed description of the best presently knownmodes of carrying out the inventions. This description is not to betaken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the inventions.

One example of a cochlear implant (or “implantable cochlear stimulator”)in accordance with at least some of the present inventions isillustrated in FIGS. 1-4B. The cochlear implant 100 includes a flexiblehousing 102 formed from a silicone elastomer or other suitable material,a processor assembly 104, a cochlear lead 106 with an electrode array108, and an antenna 110 that may be used to receive data and power byway of an external antenna that is associated with, for example, a soundprocessor unit. The electrode array 108 includes a flexible body 112 anda plurality of electrically conductive contacts 114 (e.g., the sixteencontacts 114 illustrated in FIG. 4) spaced along the curved surface 116of the flexible body. Suitable materials for the flexible body 112include, but are not limited to, LSR, high temperature vulcanization(“HTV”) silicone rubbers, room temperature vulcanization (“RTV”)silicone rubbers, and thermoplastic elastomers (“TPEs”), while suitablematerials for the contacts 114 include, but are not limited to,platinum, platinum-iridium, gold and palladium. The contacts 114 may bereferred to in numbered order, 1^(st) through 16^(th), with the contactclosest to the tip 118 being the 1^(st) contact and the contact closestto the base 120 being the 16^(th) contact. The exemplary flexible body112 also includes a longitudinally extending planar (or “flat”) surface122 that does not include conductive contacts. Once implanted, theconductive contacts 114 on the curved surface 116 face the modioluswithin the cochlea. The flat surface 122 reduces the likelihood that theelectrode array 108 will rotate after being inserted into the cochlea,as is discussed below with reference to FIG. 23. It should also be notedthat the methods of forming the electrode array described below producesmooth exterior surface transitions 124 from the flexible body 112 tothe contacts 114.

Turning to FIG. 2, in addition to the electrode array 108, the exemplarycochlear lead 106 includes a wing 126, with a rectangular portion 128and a tapered portion 130, which functions as a handle for the surgeonduring the implantation surgery. The wing 126 also provides tensionrelief for the lead wires 134, which do not run straight through thewing. A tubular member 132, which may consist of tubes of differentsizes, extends from the wing 126 to the housing 102. The contacts 114are connected to lead wires 134 (FIG. 4A) that extend through theflexible body 112 and tubular member 132 to a connector (not shown) inthe housing 102.

A positioning magnet 136 (FIG. 1) is located within a magnet pocket 138.The magnet 136 is used to maintain the position of a headpiecetransmitter over the antenna 110. The cochlear implant may, in someinstances, be configured is manner that facilitates magnet removal andreplacement. Here, the housing 102 may be provided with a magnetaperture (not shown) that extends from the magnet pocket 138 to theexterior of the housing.

Referring to FIGS. 4A and 4B, the electrode array 108 has a truncatedcircle shape in a cross-section perpendicular to the longitudinal axis A(FIG. 3) of the electrode array. The circular portion of the perimeterof the cross-section, as defined by both the outer surface of thecontacts 114 and the curved surface 116 of the flexible body 112, ismore than one-half of the perimeter of the cross-section. Put anotherway, the contacts 114 and curved surface 116 extend more than 180degrees around the longitudinal axis A of the electrode array 108. Inother implementations, the contacts 114 and curved surface 116 mayextend 130-180 degrees around the longitudinal axis A. It should also benoted here that the present contacts have a larger exposed area thanconventional contacts, which results in lower impedance and longerbattery life. The length of the flat surface 122 is less than thediameter of the truncated circle in the embodiment illustrated in FIGS.1-4B.

One exemplary method of forming an electrode array, such as theelectrode array 108 illustrated in FIGS. 1-4B, may involve the use ofthe exemplary mold 200 illustrated in FIGS. 5 and 5A. Mold 200 has firstand second mold parts 202 and 204. The first mold part 202 includes aplate 206 with a surface 207 that defines an elongate cavity 208 in theshape of the electrode array 108. Given the shape of the electrode array108, the elongate cavity 208 has a truncated circle shape in across-section perpendicular to the longitudinal axis of the cavity. Anopening 210 extends through the top surface 212 of the plate 206. Theopening 210 has a width W_(o) that is less than the maximum width M_(w)of the elongate cavity 208 and, as a result, the first mold part 202includes a pair of inwardly extending projections 209 that defineundercuts 211 (FIG. 5B).

The top surface 212 of the exemplary first mold part 202 also includesmarkers 214 that correspond to the intended locations of the contacts114 before and during the process that is described below with referenceto FIGS. 6-17. Here, there is a single marker 214 for each of thecontacts 114. In another implementation (not shown), a set of fourmarkers 214 (two on each side of the cavity 208) may be provided foreach of the contacts 114. The marker sets extend from the tip portion216 of the cavity 208 to the base portion 218 of the cavity (FIG. 6).The second mold part 204, which includes a flat bottom surface 220 thatfaces the top surface 212 (and opening 210) of the first mold part 202,will be positioned over the first mold part after the contacts 114 havebeen positioned within the cavity 208 in the manner described below. Theflat surface 220 shapes the flat surface 122 of the exemplary flexiblebody 112. The second mold part 204 also includes one or more inlets 222for the injected LSR (or other resilient material) that forms theflexible body 112.

The first mold part 202 may in some instances be a disposable partformed by a photoetching process. Although iron and other photoetchablematerials may be employed, the exemplary first mold part 202 is formedfrom copper, which is relatively inexpensive and has a number ofadvantageous properties. Copper is unlikely to bond to platinum contacts114 because copper does not weld easily and has relatively high thermalconductivity, which causes heat to dissipate very readily. Copper isalso resilient in that it will flex slightly and return to its shapewhen the platinum contact workpieces (discussed below) are pressedthrough the opening. Copper is easy to bend, which facilitates releaseof the electrode array (discussed below). Also, as copper iselectrically conductive, it may be used in an opposed weld process wherethe copper mold part 202 forms part of the electrical loop. In otherimplementations, the mold part 202 may be a reusable apparatus thatconsists of two separable pieces formed from a harder material such asstainless steel. The second mold part 204 may be reusable and formedfrom stainless steel or any other suitable hard metal.

It should also be noted that the wing 126 (FIG. 2) may be formed with astainless steel mold (not shown) which has a wing-shaped cavity and isaligned with the mold 200 during the injection process.

Turning to FIGS. 6-7D, the exemplary method includes placing a contactworkpiece 224 onto the first mold part 202 at the location defined bythe marker 214 closest to the base portion 218. Referring first to FIGS.6 and 7, the exemplary contact workpiece 224 is a tube defined by a wall226 formed from platinum or other suitable contact material. Althoughnot limited to any particular shape, the exemplary workpiece is acylindrical tube and is circular in cross-section. The diameter of thecontact workpiece 224 is greater that the width W_(o), (FIG. 5A) of theopening 210 and, as a result, the contact workpiece will not passcompletely through the opening prior to being compressed in the mannerdescribed below. In the illustrated implementation, the diameter of thecontact workpiece 224 is equal to the diameter of the cavity 208.

Turning to FIG. 7A, the contact workpiece 224 may be compressed with atweezers or other suitable instrumentality into a non-circular (e.g.,elliptical) shape by applying force F to the lateral sides of the wall226 until the width of the contact workpiece is slightly less than,equal to, or no more than slightly greater than, the width W_(o), of theopening 210. The compressed contact workpiece 224 may then be insertedthrough the opening 210 and into the cavity 208 (FIG. 7B). Theresilience of the mold part 202 will allow the opening to widen slightlyin those instances where the width of the compressed contact workpiece224 is slightly greater than the width W_(o), of the opening 210. ForceF may then be applied to the top of the compressed contact workpiece224, in the manner illustrated in FIG. 7C, to cause the contactworkpiece bulge outwardly into the original circular cross-sectionalshape or a shape close to the original circular cross-sectional shape(as shown). Here, portions of the contact workpiece 224 are locatedunder the projections 209 and within the undercuts 211. The lead wire134 that will be connected to the contact 114 formed by the workpiece224 may then be positioned within the workpiece, as shown in FIG. 7D.The portion of the lead wire 134 within the workpiece 224 may bestripped of insulation prior to the being inserted into the workpiece,or the insulation may simply be allowed to burn off during theapplication of heat and pressure to the workpiece (described below withreference to FIG. 8).

Next, as illustrated in FIG. 8, heat and pressure are applied to thecontact workpiece to form the contact 114. The contact 114 is pressedtightly against the mold surface 207 that defines the cavity 208,thereby preventing movement of the contact. The surface 207 masks theouter surface of the contact 114 and defines the outer surface offlexible body 112 in the spaces not covered by the contacts 114.Portions of the contact 114 are located under the projections 209 andwithin the undercuts 211. The compression and distortion of themalleable workpiece 224 also cause portions of the wall 226 to come intocontact with one another along a seam 230 with the lead wire 134therebetween. In some but not all instances, and as is the case in theillustrated implementation, gaps 232 may be formed between otherportions of the wall 226. The gaps 232 augment the mechanicalinterconnection between the flexible body 112 and the contacts 114, asis discussed below with reference to FIG. 16.

The steps illustrated in FIGS. 6-8 may then be repeated to form theremainder to the contacts 114. To that end, and referring to FIG. 9, thenext contact workpiece 224 may be placed onto the first mold part 202 atthe location defined by the next adjacent marker 214 in the mannerdescribed above with reference to FIGS. 7-7D. The lead wire 134 thatwill be connected to the contact 114 formed by this workpiece 224 ispositioned within workpiece and extends over the previously preparedcontact to and beyond the base portion 218 of the cavity 208. Heat andpressure are then applied to the workpiece 224 with, for example, a weldtip, such as the molybdenum weld tip 228 in a resistance weldingprocess. The heat and pressure compress the workpiece 224 against thesurface 207 that defines the cavity 208, thereby forming the secondcontact 114 (FIG. 10). This process is repeated until the last contact114 is formed in the region adjacent to the tip portion 216 of thecavity 208, as is illustrated in FIGS. 11-13.

In other implementations, the contacts 114 may be formed by compressingthe workpiece 224 with a stainless steel weld tip (no heat applied) andthen applying heat with a molybdenum weld tip, thereby preventing wearon both weld tips.

Once all of the contacts 114 have been formed and connected torespective lead wires 134, the second mold part 204 may be placed overthe first mold part 202 to complete the mold 200 in the mannerillustrated in FIGS. 14 and 15. A clamp, screws or other suitableinstrumentality (not shown) may be used to hold the mold parts 202 and204 together. The LSR or other suitable resilient material may then beinjected (or otherwise introduced) into the mold cavity 208 to form theflexible body 112. The masking effect of the mold surface 207 preventsthe resilient material from flashing over the outer surfaces of thecontacts 114. After the resilient material hardens, the mold parts 202and 204 may be separated from one another. The completed electrode array108 may be removed from the cavity 208 by, for example, bending the moldpart 202 so as to increase the width W_(o) of the opening 210 in themanner illustrated in FIG. 15A. The bent and/or broken mold part 202 maythen be disposed of.

Turning to FIG. 16, the now-completed electrode array 108 includes theaforementioned flexible body 112, contacts 114 and lead wires 134. Theflat surface 122 of the flexible body 112 does not include contacts 114or other conductive elements. The contracts 114 extend more than 180degrees around the longitudinal axis A in the illustrated embodiment. Inother embodiments, the contacts may extend 180 degrees or less aroundthe longitudinal axis A. The outer surfaces of the contacts 114 are freeof resilient material due the masking effect of surface 207. The leadwires 134 are each connected to a respective one of the contacts andpass through the open central region defined by the other contacts.Portions of the flexible body 112 are located with the contact gaps 232,thereby augmenting the mechanical interconnection between the flexiblebody 112 and the contacts 114.

The various method steps described above are summarized in the flowchart illustrated in FIG. 17. The first workpiece 224 is positioned inthe intended location within the first mold part 202, as is identifiedby the indicia 214, adjacent to the base portion 218 of the cavity 208(Step S01). A lead wire 134 is placed within the workpiece 224 (StepS02). It should be noted here that the order of steps S01 and S02 may bereversed, or steps S01 and S02 may be performed simultaneously. Theworkpiece 224 is then compressed through the use of, for example, heatand pressure applied by the weld tip 228, to form a contact 114 (StepS03). This process is repeated until all of the contacts 114 have beenformed within the mold cavity 208 (Step S04). Once all of the contacts114 have been formed, the second mold part 204 may be placed over thefirst mold part 202 (Step S05) and LSR or other resilient material maybe injected into the mold cavity 208 (Step S06). The completed electrodearray 108 may be removed from the first mold part 202 after theresilient material has cured (Step S07).

The present apparatus and methods are not limited to the exemplaryimplementation described above. In other implementations of the presentmethod, all of the workpieces 224 may be positioned within the cavity208 of the first mold part 202 without the lead wires 134. Thereafter,and beginning with the workpiece 224 closest to the base portion 218 ofthe cavity 208, a lead wire 134 may be inserted into a workpiece andthat workpiece may be compressed (e.g., with heat and pressure appliedby a weld tip) to form a contact 114. This process may be repeated untilthe last contact 114 has been formed within the cavity 208. LSR or otherresilient material may then be injected into the mold cavity 208 in themanner described above to complete the electrode array 108.

The present methods may also be used to form other electrode arrays withflat surfaces, as well as arrays with curved or otherwise non-flatsurfaces. By way of example, but not limitation, the exemplary mold 200a illustrated in FIG. 18 is substantially similar to mold 200 andsimilar elements are represented by similar reference numerals. Here,however, the second mold part 204 a includes a recess 220 a that isaligned with the opening 210 of the first mold part 202. The electrodearray 108 a (FIG. 19) produced by the mold 200 a is substantiallysimilar to the electrode array 108 and similar elements are representedby similar reference numerals. Here, however, the flexible body 112 ahas a flat surface 122 a that is a greater distance from the contacts114 than is the flat surface 122 of flexible body 112 (FIG. 16).

Turning to FIGS. 20 and 21, the exemplary mold 200 b is substantiallysimilar to mold 200 and similar elements are represented by similarreference numerals. Here, however, the first mold part 202 b includes aplate 206 b with an elongate cavity 208 b is semi-circular (i.e., 180degrees) in a cross-section perpendicular to the longitudinal axis ofthe cavity. An opening 210 b extends through the top surface 212 of theplate 206 b. The width of the opening 210 b is equal to the diameter ofthe workpiece 224. As a result, the workpiece 224 passes through theopening 210 b, and into the cavity 208 b when the workpiece is placedonto the first mold part 202 b, without the compression described abovewith reference to FIGS. 7-7D. The workpiece 224 may be compressed (e.g.,by heat and pressure applied by a weld tip) to form a semi-circularcontact 114 b, with a seam 230 b, that is connected to a lead wire 134.Once all of the contacts 114 b have been formed and connected torespective lead wires 134, the second mold part 204 may be placed overthe first mold part 202 b to complete the mold 200 b. The LSR or othersuitable resilient material may then be injected into the mold cavity208 b to form the flexible body 112 b of the electrode array 108 billustrated in FIG. 22. The electrode array 108 b is substantiallysimilar to the electrode array 108 and similar elements are representedby similar reference numerals. Here, however, the flexible body 112 ahas a flat surface 122 a with a width that is equal to the diameter ofthe semi-circular electrode array 108 b, which allows the electrodearray 108 b to be removed from the mold part 202 b without bendingand/or destroying the mold part.

As illustrated for example in FIG. 23, the exemplary electrode array 108may be positioned within the scala tympani ST of the cochlea C in such amanner that the flat surface 122 of the flexible body 112 is facing thelateral wall LW and the contacts 114 are facing the medial wall MW. Someor all of the flat surface 122 is positioned against the lateral wallduring insertion of the electrode array 108 into the cochlea, therebyreducing the likelihood that the electrode array will twist. Preferably,the flat surface 122 remains against the lateral surface LW for theentire insertion process, i.e. from the entry of the tip 118 into thecochlea by way of the round window (or a cochleostomy), to the point atwhich the portion of the electrode array 108 with the contacts 114 haspassed through the round window (or cochleostomy) and is within thecochlea. The contacts 114 and the curved surface 116 of the flexiblebody 112 face the modiolus within the cochlea and the medial wall MWduring (as well as after) insertion.

It should be noted that the present apparatus and methods are notlimited to electrode arrays with a flat surface. To that end, andreferring to FIG. 24, the exemplary mold 200 c is substantially similarto mold 200 and similar elements are represented by similar referencenumerals. Here, however, the second mold part 204 c includes a recess220 c that is aligned with the opening 210 of the first mold part 202.The recess 220 c has a radius of curvature that is equal to that of therecess 208. Thus, when combined, the recess 208 and the recess 220 cdefine a circle in a plane perpendicular to the longitudinal axis of therecess 208. The electrode array 108 c (FIG. 25) produced by the mold 200c is substantially similar to the electrode array 108 and similarelements are represented by similar reference numerals. Here, however,the electrode array 108 c defined by the flexible body 112 c and thecontacts 114 is circular in cross-section. The exemplary electrode array108 c may be positioned within the scala tympani ST of the cochlea C inthe manner illustrated in FIG. 26.

Although the inventions disclosed herein have been described in terms ofthe preferred embodiments above, numerous modifications and/or additionsto the above-described preferred embodiments would be readily apparentto one skilled in the art. By way of example, but not limitation, theinventions include any combination of the elements from the variousspecies and embodiments disclosed in the specification that are notalready described. It is intended that the scope of the presentinventions extend to all such modifications and/or additions and thatthe scope of the present inventions is limited solely by the claims setforth below.

We claim:
 1. A cochlear implant, comprising: a housing; an antenna within the housing; a stimulation processor within the housing operably connected to the antenna; and an electrode array, operably connected to the stimulation processor, including a flexible body defining a longitudinal axis and a truncated circle shape in a cross-section perpendicular to the longitudinal axis, and a plurality of electrically conductive contacts on the flexible body that extend uninterruptedly more than 180 degrees around the longitudinal axis.
 2. A cochlear implant as claimed in claim 1, wherein the flexible body includes a curved surface and a flat surface; and the electrically conductive contacts are located on the curved surface of the flexible body and have a surface that defines a partial circle which extends uninterruptedly more than 180 degrees around the longitudinal axis.
 3. A cochlear implant as claimed in claim 2, wherein there are no electrically conductive contacts on the flat surface.
 4. A cochlear implant as claimed in claim 2, wherein the flexible body defines a diameter; and the flat surface defines a width that is less than the diameter.
 5. A cochlear implant as claimed in claim 2, wherein the flexible body defines a diameter; and the flat surface defines a width that is equal to the diameter.
 6. A cochlear implant as claimed in claim 1, wherein the electrode array is formed by a method comprising the steps of: positioning a workpiece on a mold part with a channel having an undercut such that a portion of the workpiece is within the channel of the mold part; compressing the workpiece to form a contact; and introducing resilient material into the channel to form a flexible body.
 7. A cochlear implant as claimed in claim 6, wherein the method further comprises the step of positioning a lead wire within the workpiece prior to the step of compressing the workpiece.
 8. A cochlear implant as claimed in claim 6, wherein the workpiece comprises a tubular workpiece.
 9. A cochlear implant as claimed in claim 6, wherein wherein the mold part comprises a first mold part; and the method further comprises the step of positioning a second mold part over the first mold part such that a flat surface of the second mold part covers the inlet.
 10. A cochlear implant as claimed in claim 6, wherein the step of compressing the workpiece comprises applying heat and pressure to the workpiece.
 11. A cochlear implant as claimed in claim 6, wherein the channel is defined by a surface of the mold part; and the step of compressing the workpiece comprises compressing the workpiece against a portion of the mold part surface such that the portion of the mold part surface forms a mask over an outer surface of the contact that prevents the resilient material from covering the outer surface of the contact during the introducing step.
 12. A cochlear implant, comprising: a housing; an antenna within the housing; a stimulation processor within the housing operably connected to the antenna; and an electrode array, operably connected to the stimulation processor, including a flexible body defining a longitudinal axis and a truncated circle shape in a cross-section perpendicular to the longitudinal axis, a plurality of lead wires extending through the flexible body, and a plurality of electrically conductive contacts on the flexible body that each include first and second wall portions in contact with one another along a seam, which is arcuate in a plane perpendicular to the longitudinal axis, with a portion of one of the lead wires therebetween.
 13. A cochlear implant as claimed in claim 12, wherein the electrically conductive contacts include gaps between the first and second wall portions adjacent to the seam; and portions of the flexible body are located within the gaps.
 14. A cochlear implant as claimed in claim 12, wherein the flexible body includes a curved surface and a flat surface; and the electrically conductive contacts are located on the curved surface.
 15. A cochlear implant as claimed in claim 14, wherein there are no electrically conductive contacts on the flat surface.
 16. A cochlear implant as claimed in claim 15, wherein the electrically conductive contacts extend more than 180 degrees around the longitudinal axis.
 17. A cochlear implant as claimed in claim 14, wherein the flexible body defines a diameter; and the flat surface defines a width that is less than the diameter.
 18. A cochlear implant as claimed in claim 14, wherein the flexible body defines a diameter; and the flat surface defines a width that is equal to the diameter.
 19. A cochlear implant as claimed in claim 12, wherein the first and second wall portions are both in contact with the portion of the wire therebetween. 